The aim of this dissertation is to present further information on the effects of boars' seminal plasma on sperm motility and female genitals, while paying particular attention to the boars' characteristics. On this occasion the seminal plasma was tested with regard to practical applicability as an additive to boar semen diluents in liquid form. The first series of tests served to analyse the effect of seminal plasma exchange among ejaculates of two boars on the sperm motility in vitro and mating ability in vivo. The effects on sperm motility were examined in a thermostability test. Furthermore, gilts were inseminated with sperm of either a good or a bad service boar with an additive of homologous or heterologous seminal plasma in the diluent. Success of fertility was determined by the number of recovered ova and embryos. In the course of the test, faeces were taken from the gilts to determine the P4\- progesteronecontent. That was carried out to observe reactions of gilts to the application of seminal plasma from good or bad service boars and of ovulation synchronisation. The objective of the second series of tests was to characterize the effect of a determinate part of seminal plasma in the fluid-preserved semen of boars on sperm motility and fertilisation results, whereby boar specificity was also considered. Ejaculates from five boars were used in the preliminary test for this, having first been treated with diluents containing 0 %, 10 %, 20 % or 40 % seminal plasma. In field trials 196 sows were inseminated with semen, which had been preserved with diluents containing either some 40 % or no seminal plasma. In the first part of the trial we additionally used seminal plasma from nine sires, which were good service boars in practice. In the second part we used seminal plasma from only one boar, whose seminal plasma in previous experiments had shown a constant stimulating effect on the motility of foreign sperm. We subsequently obtained the following results:
* Homologous and heterologous seminal plasma can have different effects on the portion of movable sperms. Seminal plasma from ejaculates with a high sperm motility enhanced the motility of foreign sperms and was superior to diluents containing no seminal plasma with regard to the effect on activity of movement by sperm cells. * Inseminations of gilts with the sperm of both good and poor service boars, which had been preserved with diluents, which contained 30 % seminal plasma of a good service boar, resulted in high conception rates (70,1 (31,3) %or rather 77,7 (19,6) %). When seminal plasma from a poor service boar was used as an additive for diluents, only inseminations with such preserved homologous sperms obtained similar high conception rates (82,9 (29,2) %). The conception rate of sows, which were inseminated with preserved homologous sperms through the above mentioned mix of seminal plasma and diluent, was only 53,0 (34,7) %. Differences have not been proved by statistics (-> = 0,05). * These insemination attempts shared that with P4- progesterone-determination in faeces, it is possible to obtain information about the cycle activity of sows and to check the activity of corpus luteum. No connexion was found between the application of seminal plasma from good and poor service boars and the excretion of progesterone through faeces. * In laboratory experiments the additive of seminal plasma to diluent showed a positive effect on sperm motility when stored for 72 hours. In these studies no significant differences were found between the various seminal plasma portions in diluent (10 %, 20 %, 40 %). When ejaculates from routine sperm production were used, a generally stimulating effect of seminal plasma additives to diluent (seminal plasma 40 %) on sperm motility could only be shown during a storage period of about 24 hours. Only the seminal plasma of a determinate boar which clearly and constantly stimulated sperm motility had a significantly positive effect after 72 hours. * The insemination of adult sows with semen, which had been preserved with diluents containing either some or no seminal plasma achieved good results as regards farrowing rates (experimental ratio 1: 88,3 % or rather 85,7 %; experimental ratio 2: 90,5 % or rather 85,7 %), piglet indices (experimental ratio 1: 838,6 or rather 762,7; experimental ratio 2: 760,2 or rather 771,3) and product of the farrowing rate and the size of the litter (experimental ratio 1: 856,5 or rather 797,0; experimental ratio 2: 760,2 or rather 814,2). There are no significant differences. Tendentiously positive effect of a seminal plasma additive to diluent were only seen in the size of litter (+ 1,1) in the experimental ratio 2.